assoc_instead_of_hash.rb

# Using Array#assoc instead of a Hash when comparing using only ==

require 'test/unit/assertions'
include Test::Unit::Assertions

class Foo
  def initialize(i)
    @i = i
  end

  attr_reader :i

  def ==(other)
    @i == other.i
  end
end

foo_1  = Foo.new(1)
foo_1b = Foo.new(1)
foo_2  = Foo.new(2)

assert_not_equal foo_1, foo_2
assert_equal foo_1, foo_1b

# We can't use hash grouping ability because the class Foo does not properly
# implement #hash

i_counter = Hash.new(0)
[foo_1, foo_1b, foo_2].each do |foo|
  i_counter[foo] += 1
end

begin
  assert_equal 2, i_counter[foo_1]
  assert_equal 1, i_counter[foo_2]
rescue MiniTest::Assertion
  p $!
end

# Array#assoc to the rescue :)

i_counter = []
[foo_1, foo_1b, foo_2].each do |foo|
  assoc = i_counter.assoc(foo)
  if assoc
    assoc[-1] += 1
  else
    i_counter << [foo, 1]
  end
end

assert_equal 2, i_counter.assoc(foo_1).last
assert_equal 1, i_counter.assoc(foo_2).last